Setting outbound packet priority / packet scheduling / packet queueing is generically known by the phrase, "Traffic Shaping." With OpenBSD, this is done via the pf(4) facility. The particulars are described in the PF User's Guide (www.openbsd.org/faq/pf/index.html) in the chapter titled: "Packet Queuing and Prioritization". Here's a link to that chapter: http://www.openbsd.org/faq/pf/queueing.htm

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By "PTP", do you mean the Microsoft PPTP protocol? There are two 3rd party packages: